Fuel burning apparatus



I July 21, 195 9 E. c. MILLER FUEL BURNING APPARATUS Filed Jan. 23, 1956 4 Sheets-Shed 1 Hi 1 u Z43 5,) I I1 I 34 Z0 "If 2 ar III 10 [l INVENTOR.

EARLE C. MILLER ZW W E. C. MILLER FUEL BURNING APPARATUS July 21, 1959 4 Sheets-Sheet 2 FiledJan. 23, 1956 Fig.2

INVENTORn Exams 6 MILLER BY WW j I r/ I July 21, 1959 E; c. MILLER FUEL BURNING APPARATUS Filed Jan. 23, 1956 1 I I a [I I l I ,7 m I l I I .l 1 .I I I 2 1 I I I I I I I V 1 h, 1 I I I 6 I 5 I I 1 1 I I I. I H N I I 1 I I l I I I I 1 11/ 1111/! 11/! 11111 I, IIIIIIIII INVENTOR. [A1245 6. MILLER BY I y 21, 1959 E. c. MILLER 2,895,436

' FUEL BURNING APPARATUS Filed Jan. 23, 1956 4 Sheets-Sheet 4 'INVENTOR. E4245 6. MILLER Stoker Corporation, Worcester, Mass, a corporation of Massachusetts Application January 23, 1956, Serial No. 560,562 a clai s. Cl. 110-165 This invention relates to fuel burning apparatus and more particularly to apparatus arranged to return flyash or like to the main combustion chamber of a steam generating unit.

In the operation of steam generating apparatus, a considerable amount of unburned fuel is sometimescarried over into the boiler elements and would be carried up the smokestack if it were not for collecting apparatus associated with the equipment. This is particularly true when fuel is projected into the combustion chamber by means of a spreader stoker or the like, and, of course, the situation exists to an even greater degree, when the fuel being burned is a refuse fuel, such as bagasse or wood bark. In any case, it is desirable to return such flyash, cinders, and the like to the main combustion chamber, sincethey usually contain a high percentage of combustible material. Furthermore, the flyas'h must be disposed of some way, and the best way to cause it to flow into the ashpit instead of goingthrough the stack into the air is to return it to the main combustion chamber. In the past this has been done in many instances by projecting it into the combustion chamber mixed with a stream of air. This has the disadvantage, however, that flyash introduced into the combustion chamber in this way is very likely to be carried in suspension into the. boiler portions of the apparatus in the same way as before. It would be preferable to lay the flyash in a blanket on the'main grate of the furnace to act as a bed for the introduction of fresh fuel and to protect portions of the grate on which fresh fuel was not being added for one reason or another. 'Attempts to introduce the flyash to the main combustion chamber in this manner have in the pastbeenrelatively unsuccessful. The deficiencies of the prior art havebeen obviated by the present invention in a novel manner.

It is therefore an outstanding object of the invention to provide a fuel burning apparatus in which flyash is introduced into the combustion chamber of a steam generating unit in the form of a blanket laid on the'surface of the main grate.

Another object of this invention has the provisionof means for introducing flyash into the combustion chamber of a steam generating unit by which means very little of the flyash is permitted to be carried over into the boiler.

It is another object of the present invention to provide a fuel burning apparatus having novel means for distributing flyash onto one end of a grate.

A still further object of the instant invention is the provision of a fuel burning apparatus comprising a spreader stoker firing onto an oscillating grate in which provision is made for the reinjection of fiyash in much a manner that it is not carried upward in the furnace with the combustion gases.

Another object of the invention is the provision of a fiyash reinjection means 'whic'h is reliable in operation, inexpensive to manufacture, and simple to maintain.

With these and other objects in view as, will be apparent to those skilled inthe 'art the inventionresides in'the nited States Patent ice 2 combination of parts set forth in the specification and covered bythe claims appended hereto.

The character of the invention, however, may be best understood by reference to certain of its structural forms as illustrated by the accompanying drawings in whichi Figure l is alongitudinal sectional view of a steam generating apparatus embodying the principles of the present invention,

Figure 2 is a transverse sectional view of the apparatus shown in Figure 1 taken on the line IIII thereof.

Figure 3 is an enlarged view of a portion of Figure 2,-

Figure 4 is a sectional view of the apparatus shown in Figure 3 taken on the line IVIV,thereof.

Figure 5 is a sectional view of a steam generating unit embodying the principles of a modification of the invention, and

Figure 6 is a plan view ofa portion of the apparatus shown in Figure 5.

In the specification which follows, the expression 1ongitudina and the like is used, to indicate the, direction of general flow of gas in the steam generating unit, that is to say, in the plane of the drawing of Figure 1, whereas the expression transverse indicates a direction transverse to the flow of gas in the steam generating unit as isillustrated by the plane of the drawing in Figure 2.

Referring first to Figure 1, wherein is bestshown the general features of the invention, the fuellburning apparatus of the invention, indicated generally by thefreference numeral 10, is shown in use in connection with a furnace 11 and a boiler 12. The furnace 11 consists of a front wall 13, a roof 14, and side walls '15 serving to define a combustion chamber 16. The boiler 12 consists of a steam and water drum 17, a mud drum 18, and boiler tubes 19 arranged in the usual manner. An opening 20 is formed in the front wall 13, of the furnace and mounted on the wall in front of this opening is a spreader stoker 21 of the general type shown and described in the patent to Miller, No. 2,538,944. A fuel bunker 22 overlies the spreader stoker and is joined to it by a conduit 25. In the lower part ofthe combustion chamber 16 is mounted an oscillatinggr ate 24 of the type generally shown and described in the patentJapplication ofjOllison Craig, Serial No. 460,399, filed October 5, 1954, now abandoned. This grate is provided with anupper grate surface 25 provided with a large'number of perforationsfor the flow therethrough of combustion "air. This is connected by resilient plate members 26 to a base 27 mounted on the foundation of a steam generatingunit. Underlying the entire grate is an air plenum chamber 28 suitably connected to a forced draft fan, not shown. Underlyingjthe forward end of the grate 24 andthe front wall 13 of the furnace is an ashpit 29. The rearward end of the grate 24 is provided with a solid portion .30 having a fiat upper surface, whichportion is not provided with perforations nor provided with forced draft means of any kind. The grate 24 ,is driven by am'otor 32 driving an eccentric 33 whereby the grate. is caused to vibrate and to move fuel or ash lying on its surface forwardly so that-it eventually drops into the ashpit 29. Some of the tubes. of the boiler 12 are formed, into an arch 34 which overlies the rearward portion 30 of the grate 24. Alternate tubes of thearch 34 are arranged above and below each other to give the arch considerablethickness and a heavy layer of refractory is placed between the tubes. A refractory baflie 35 extends angularly across the ,tubes of the boiler to define withthe arch :34 a recess 36 in which lies a transverse tray 37. It should be noted that the boiler is arranged to transmit the products of combustion leaving the tubes 19 to a dust collector 38,the exit of whichis connected through a fate. the stack, .as will be described subsequently.

Referring now to Figure 2, it can be seen that the tray 37 extends outwardly of the boiler 12 and is com nected by a conduit 39 to the dust collector 38. It is evident in this view that the exit of the dust collector is connected to an induced draft fan 41 which in turn is connected to a breeching 42 leading to the smokestack. It should be noted that a motor-driven star feeder 43 is connected between the ash disposal end of the dust collector 38 and the conduit 39' leading to the tray 37.

Referring next to Figure 3 which shows an enlarged view of the tray 37, in the same aspect shown in Figure 2, it may be observed that the tray is mounted on re silient inclined plate members 44 and is caused to vibrate by means of an eccentric 45 mounted with its axis longitudinal of the furnace and driven by a motor 46. The lowe'r' end of the conduit 39 is connected to the tray by means of a flexible hood 47 formed of rubber or the like. In the plan view of the tray shown in Figure 4, it can be seen that the tray consists of a bottom 48 which is cut at an angle along the line 49, of an end wall 51 adjacent the entrance of the conduit 39, a back wall 52, and the forward wall 53. An end structural member 54 is provided to give the structure rigidity. Rib 'walls 56 and 57 divide the longitudinal dimension of the tray into three equal parts and a top wall 58 is provided to prevent dust or ash from rising from the tray. It is to be observed that the ribs 56 and 57 intersect the line 49 at widely spaced points transversely of the furnace. The edge 49, the end member 54, and the side wall 53 form a triangular opening space 59, the point of intersection of the line 49 and the side 53 being arranged to be adjacent one side of the furnace, while the side of the triangle defined by the member 54 is arranged to lie on the other side of the furnace so that the triangle subtends the entire width of the furnace.

The operation of the invention will now be readily understood in view of the above description. Fuel from the bunker 22 passes through the conduit 23 into the spreader stoker 21 and is projected into the combustion chamber 16. Some of the particles of fuel being very light are caught up in the flow of gas upward through the combustion chamber and are burned in suspension, while the heavier particles of fuel fall onto the grate 24. These heavier particles fall onto the grate surface 25 and combustion air passes from the plenum chamber 28 upwardly through the apertures in the grate surface causing combustion of the fuel. Products of combustion pass up wardly through the combustion chamber 16 and through the boiler 12 in heat exchange relationship to the tubes 19. From there they pass into the dust collector 38 where the dust and combustion gas are separated, the gas flowing through the fan 41, into the breeching 42, and up the smoke stack. The dust, coal particles, ash, flyash, cinders, and the like collect in the bottom of the dust collector. It should be noted that under the action of the motor 32 and the eccentric 33 the grate 44 is subjected to an oscillating or vibrating action of fairly low frequency. This causes any fuel, ash, or other particles residing on the grate surface 25 to move forwardly along the grate and eventually to be discharged from the forward end of the grate into the ashpit 29. The feeder 43 releases flyash regularly into the conduit 39 so that it falls downwardly through the conduit into the tray 37. The tray 37 is vibrating transversely of the furnace under the action of the motor 46 and the eccentric 45. The plates 44 are inclined in such a direction that the movement of ash along the tray transversely of the furnace is away from the conduit 39 and toward the triangular cutout portion 59. The ash divides itself fairly evenly between the three passages lying between the upper cover 58 and the bottom 48 of the tray lying between the side wall 52 and the rib wall 56 between'the rib 56 and the rib wall 57 and between the rib wall 57 and the forward wall 53. Eventually the flyash reaches the edge 49 and falls downwardly through the trinagular section 59. The triangular section 59 overlies the solid rearward portion 30 of the grate 24 and suitable apertures are previded through the arch 34 for the passage of flyash downwardly between the tray and the rearward portion 30. Flyash. falls onto the readward portion 30 and immediately begins its travel forwardly along the grate surface. Since: the portion 30 is not provided with an under-grate air source or with apertures of any kind, the ash lies quietly on its surface and forms a blanket. Eventually this blanket moves forward into the lower part-of the com-- bustion chamber 16 and on to the grate surface 25. At that time fresh fuel originating in the spreader stoker 21' falls on the surface of the blanket of flyash and tends to keep it fixed on the grate surface. Air passing upwardly through the grate surface 25 causes combustion of any material in the flyash which has not already been burned- Eventually the flyash passes into the ash pit 29.

It should be observed that if it is desired to lower the amount of fuel being burned in the combustion chamber 16, that is to say, to lower the load of the steam generating unit, this may be done by regulating the spreader stoker 21 in such a manner that only a portion of the grate, preferably the front portion, is being used for the burning of fresh fuel. In the portion of the grate thus used, the fresh fuel is projected in a layer thick enough to maintain good combustion, whereas if the lower amount of fuel were spread over the entire grate, there would be insufficient concentration at any part of the grate to give good combustion and proper ignition. If, however, this cutoff method is used, ordinarily the rearward portion of the grate on which fresh fuel was not being projected would be bare and liable to be burned out because of the fact that it resides in a very hot combustible chamber. When the present method of flyash reinjection is used, however, a layer of flyash and cinders lies on this rearward portions of the grate at all times and protects the grate from damage.

Referring next to Figures 5 and 6, wherein is shown a modified form of the invention, a fuel burning apparatus, designated generally by the reference numeral 110, is shown in use with a furnace 111 and a boiler 112 shown only in part. The furnace 111 has a combustion chamber 113 and a spreader stoker 114 mounted on the front Wall thereof. A suitable plenum chamber 115 is provided as well as an ash pit 116. A vibrating grate 117 having an upper surface 118 mounted on resilient plates 119 underlies the combustion chamber 113. The grate 117 is suitably driven from a motor 121 which drives an eccentric 122 mounted on the underside of the grate. The boiler 112 is provided with cinder collecting hoppers 123 and 124, preferably located at points of reversal of gas flow within the boiler. A suitable arch 125 is formed by the boiler tubes and overlies the rearward portion of the grate 117. On the rearward portion of the grate 117 is mounted a tray 126, the plan view of which is shown in Figure 6. This tray comprises a rectangular bottom 127, end walls 128 and 129, a rearward wall 131, and a forward wall 132. It should be noted that the forward wall 132 extends along the front edge of the tray only in a portion thereof which extends outwardly of the furnace width. In other words, the front part of the tray is open in the portion thereof which lies within the furnace 113. A rib wall 132 extends from the for ward edge of the end wall 129 to the rear wall131 at a point opposite the greatest transverse extent of the wall 132. Rib walls 133 and 134 have ends which lie coextensive with the forward wall 13" and parallel thereto. As the ribs 133 and 134 extend transversely ofthe furnace along the tray, they then become inclined forwardly and eventually reach the front edge in such a manner that the distance between the end 135 of the wall 132 and the end wall 129 is divided into three equal parts by the rib walls 133 and 134. The cinder hoppers 123 and 124, as well as any other dust and ash collecting equipment, are conected by a forwardly-inclined conduit 136 which has at its forward end a funnel 137 which is directed through wall of the arch 125 and overlies the portion of the tray 126 which is adjacent the end wall 123. Flyash reaching this part of the tray is mounted on the rearward end of the grate 117 and is subjected to the vibrations originating in the eccentric 122. Even though these vibrations are for the most part longitudinal of the furnace, there will be a lateral component suflicient to move fuel transversely of the furnace within the tray 126. The fuel will be divided into three substantially equal portions by the ribs 133 and 134 and will eventually reach the forward edge of the tray in the portion which is not protected by the front wall 132 and will move forwardly onto the main grate surface 118. The flyash will move over the grate to the forward portion and fall into the ashpit 116 after a considerable portion of the combustible material therein is burned.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, de sired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described what is claimed as new and desired to secure by Letters Patent is:

1. Fuel burning apparatus comprising a self-cleaning longitudinally-extending grate, a horizontal tray located over the grate, means for collecting flyash, means for introducing the collected flyash onto the tray, means subjecting the tray to oscillatory movement transversely of the grate, the tray having a substantially flat bottom terminating in an open edge extending generally transversely over one end of the grate, the oscillatory movement of the tray causing the flyash to pass over the said edge of the tray onto the grate.

2. Fuel burning apparatus comprising a self-cleaning longitudinally-extending grate, an elongated horizontal tray extending transversely over one end of the grate, means for collecting flyash and introducing it onto one end of the tray, means subjecting the tray to oscillatory movement transversely of the grate, the tray having a substantially flat bottom terminating in an open edge extending generally transversely over one end of the grate, and rib walls extending from the said one end of the tray to the said edge, the oscillatory movement of the tray causing the flyash to pass between the ribs and over the said edge of the tray onto the grate.

3. Fuel burning apparatus comprising a self-cleaning longitudinally-extending grate of the vibrating type, a horizontal tray located over the grate, means for collecting flyash and introducing it onto the tray, means subjecting the tray to oscillatory movement transversely of the grate, the tray having a substantially flat bottom terminating in an open edge extending generally transversely over one end of the grate, the vibration of the tray causing the flyash to pass over the said edge of the tray onto the grate.

4. Fuel burning apparatus comprising a spreader stoker, a self-cleaning longitudinally-extending grate of the vibrating type onto which the stoker projects fuel, a horizontal tray located over the grate, means for collecting flyash and introducing it onto one end of the tray, means subjecting the tray to oscillatory movement transversely of the grate, the tray having a substantially flat bottom terminating in an open edge extending generally transversely over one end of the grate, the oscillatory movemerits of the tray causing the flyash to pass from the said one end of the tray and over the said open edge of the tray onto the grate.

5. Fuel burning apparatus comprising a longitudinallyextending vibrating grate, a furnace arch located over one end of the grate, a horizontal tray located within the arch and over the grate, apertures extending through the arch below the tray, the end of the grate over which the tray lies being of solid construction and non-perforated, means for collecting flyash and introducing it onto the tray, means subjecting the tray to oscillatory movement transversely of the grate, the tray having a substantially flat bottom terminating in an open edge extending generally transversely over one end of the grate, the oscillatory movement of the tray causing the flyash to pass over the said edge of the tray, through the arch, and onto the grate.

6. Fuel burning apparatus comprising a longitudinallyextending vibrating grate, a horizontal tray fastened to one end of the grate, means for collecting flyash and introducing it onto the tray, means subjecting such tray to the vibratory movements of the grate, the tray having a substantially flat bottom terminating in an open edge extending transversely over one end of the grate, ribs extending across the tray at an acute angle to the said edge to lead the flyash to the said edge, the vibratory movements of the tray causing the flyash to pass over the said edge of the tray onto the grate.

7. Fuel burning apparatus comprising a longitudinallyextending vibratory grate, a furnace arch located over one end of the grate, an elongated horizontal tray extending transversely over the said one end of the grate, means for collecting flyash and introducing it onto one end of the tray, means subjecting the tray to vibratory movement transversely of the grate, the tray having a substantially flat bottom terminating in an open edge extending generally transversely over one end of the grate, and rib walls extending from the said one end of the tray to the said edge, the vibratory movement of the tray causing the flyash to pass between the ribs and over the said edge of the tray onto the grate.

8. Fuel burning apparatus comprising a self-cleaning longitudinally-extending grate, an elognated horizontal tray extending transversely over one end of the grate, means for collecting flyash and introducing it onto one end of the tray, means subjecting the tray to oscillatory movement, the tray having a substantially flat bottom terminating in an open edge extending generally transversely over one end of the grate, and rib Walls extending from the said one end of the tray to the said edge, the oscillatory movement of the tray causing the flyash to pass between the ribs and over the said edge of the tray onto the grate.

References Cited in the file of this: patent UNITED STATES PATENTS 2,078,640 Segar Apr. 27, 1937 2,110,452 Moyer Mar. 8, 1938 2,136,951 Overstrom Nov. 15, 1938 2,186,652 Orth et a1. Jan. 9, 1940 2,592,701 Jackson Apr. 15, 1952 2,733,912 Newcomb et al Feb. 7, 1956 2,763,220 Becker et al Sept. 18, 1956 

